2004 touran warm starting problem

a couple of month`s back i had to replace the engine in my 2004 touran, i replaced it with a second hand unit and all is fine apart from the warm starting problem that i have aquired with it. my engine code is avq and the engine was replaced with another avq coded engine, i have replaced the glow plugs and it is still the same. i did notice when fitting that the fuel pump on the second hand engine i purchased was a bosch and the original pump is a luk could this be the problem?

if you turn the engine over for about 5 second stop and then try again it will start almost straight away which leads me to think that the pump could be the problem.